An apparatus, assembly and method for controlling release of a drug from a drug-eluting balloon during delivery of a drug-eluting balloon to a situs within a body. More particularly, the present invention relates to a diametrically expandable sleeve having a first non-diametrically unexpanded state in which drug retained on or in a drug-eluting balloon is protected from release by a sleeve and a second diametrically expanded state in which drug retained on or in the drug-eluting balloon is exposed for focal release in the body by diametric expansion of the sleeve, exposing openings in the sleeve during diametric expansion and closing the openings in the sleeve when the sleeve is in its diametrically unexpanded state.